Directional phase shifter



Aug. 21, 1956 Filed Dec.

A. G- FOX DIRECTIONAL PHASE SHIFTER Z'Sheets-Sheet l /86 P4 [37 I B 1LINVENTOR A. G. FOX

ATTORNEY A. G. FOX

DIRECTIONAL PHASE SHIF'TER Aug. 21, 1956 2 Sheet s-Sheet 2 Filed Dec.-27, 1951 FIG. 4

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' lNl/EN TOR A. 6. FOX

A7/ZZQNEY plied by a Faraday-effect element.

,n u DIRECTIONAL PHASE SHIFTER Arthur. G. Fox, Eatontown, N. J.,assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y.,a

This invention relates to electromagnetic wave transmission systems and,more particularly, to directional phase shifting devices havingnon-reciprocal phase :properties.

In electromagnetic wave transmission systems, it would be desirable innumerous applications to introduce a first value of phase shift toenergy traveling in one direction through the system and a second anddifferent value of phase shift to energy traveling in the oppositedirection of transmission therethrough. For example, in a repeatersystem in which one set of components serves jointlyfor communication intwo directions, say in one directionzfor transmission and in the otherfor reception or for communication in one direction at a first frequencyand in the opposite direction at a different frequency, it would bedesirable to separately equalize the phase characteristics of the systemfor each direction of transmission. Heretofore, however, it has beenextremely diflicult, if not impossible, to obtain such a non-reciprocalvalue of phase shift.

It is an object of the invention to introduce a nonreciprocal phaseshift to energy conveyed along a microwave transmission path.

It is a further object of the invention to introduce a phase shift orphase delay to energy traveling in one direction along a microwavetransmission path Without introducing a corresponding phase shift orphase delay to energy traveling in the opposite direction along saidpath.

It is a more specific object of the invention to introduce a firstpredetermined value of phase shift to wave energy traveling in onedirection along a microwave transmission path and to introduce a secondand different pre' determined value of phase shift to energy travelingin the opposite direction therealong.

In the specific embodiments in accordance with the invention to behereinafter described in detail, the nonreciprocal property of the phaseshifting device is sup- As will be shown, this element rotates thepolarization of the electric vector of electrical energy passing throughit with respect to reflecting elements interposed along the path,whereby electrical energy traversing the device in one direction will bereflected along a different path length, experiencing a different phasedelay, from the path length and phase delay of energy traversing thedevice in the opposite direction.

These and other objects, the nature of the present invention, itsvarious features and advantages, will appea-v more fully uponconsideration of the various specific il' lustrative embodiments shownin the accompanying drawings and of the following detailed descriptionof these embodiments.

I -.In the drawings:

'Fig; 1 is a perspective view of a phase shifter,'-in accordance withthe invention, introducing a predetermined unidirectional phase shift toelectrical energy traversing therethrough;

;.,Fig. 2 is a diagrammatic representation of the path United StatesPatent 2,760,166 Pa'tented Aug. 21, 1956 2- lengths followed byelectrical energy traversing the device of Fig. 1, given for the purposeof explanation;

Fig. 3 is a perspective view of aphase shifter, in accordance with theinvention, introducing separately addevice in two directions;

Fig. 3A represents an alternative modification of 3 in accordance withthe invention; and r Fig. 4 is a diagrammatic representation of the pathtric vector, which determines the plane of polarization 1 pled to guide12 by guide 11 will not be affected by vane of the wave, is parallel tothe short side of the rectangular wave guide. By means of the smoothtransition from the rectangular cross-section of either guides 11 or 13to circular cross-section of guide 12, the TElO mode goes over fromeither guide 111 or 13 into TEn mode in circular guide 12. Thedimensions of these guides are preferably chosen so that only thedominant mode in each can be propagated. Positioned in the end of guide12 adjacent guide 11 is a highly conductive reflecting vane 14 which maybe several wavelengths in length and is diametrically disposed in guide12 in a plane perpendicular to the electric polarization in guide 1 1 soas to reflect waves having their plane of polarization perpendiculartothepolarization in guide 11. Vane 14, is held in this position andadapted for longitudinal position adjustment along the length of guide12by means of thumbscrew studs 15 and 16 extending, respectively, throughopposite slots 17 and 18 in the wall of guide 12. Located a distance a;alongguicle 12 from vane 14 is a second reflecting vane 19, disposed inguide 12 in a plane 45 degrees inclined to the plane of vane 14. Exceptfor the angle of disposition, vane 19 is similar in all respects to vane.14, being heldin position by thumbscrew, studs 20 and 2-1, extendingthrough oppositely through the polarization-selective terminalcomprising guide 11. Vane 14 is a polarization-selective reflectingtermination by which only the TE11 mode of wave energy in guide 12having a polarization orthogonal to the TEu mode therein to which guide11 is coupled, is reflected by the vane ,14. Wave energy polarizedperpendicular to this reflecting polarization, i. e., perpendicular tothe plane of vane 14, may pass. along the guides in either directionunaffected by vane 14. Thus, vane 14 and .wave guide 11 constituteconjugate termini of guide 12 in that wave energy for which vane 14 iseffective will not be affected by guide 11 and, conversely, wave energycou- 14. The vane 19 and guide 13 at the other end of guide 12constitute a like'reflecting termination and connecting terminal,respectively, having, however, their respective planes of reflection andcoupling displaced by a 45 degree angle from the corresponding planes ofvane 14 and justable phase shifts to electrical energy traversing the issuitable means of the type which. produces. an anti;

reciprocal rotation of the plane of polarization of theseelectromagnetic waves, in other words, a Faraday-effect element havingsuch properties that an. incident wave impressed upon a first side ofthe, element emerges on the second side polarized at a different anglefrom the original'wave and an incident wave impressed upon the second.side emerges upon the first side with an additional rotation of thesameangle. Thus, the polarization of'a wave passing through theelement'fi'rst in one direction and then in the other undergoestwosuccessive space rotations or space phase shifts in the same sense,thereby doubling the rotation or phase shift undergone in a singlepassage. I As illustrated by way of example in the drawing, this meanscomprises a Faraday-effect element 24 with accompanying'conicaltransition members 25 and 26, which may be of polystyrene and are'provided to cut down reflections from the face of element 24, mountedinside guide 12 approximately mid-way between vanes 14 and 19. As aspecific embodiment, element 24 may be a block of magnetic material, forexample, nickel-zinc ferrite prepared inthe manner disclosed in thecopending application of C. L. Hogan, Serial No. 252,432, filed October22, 1951, having a thickness of the order of magnitude of an inch. Thismaterial has been found to operate satisfactorily asadirectionally'selective Faraday-eflect rotator for polarizedelectromagnetic waves to an extent up to 9 degrees or morewhen placed inthe presence of a longitudinal magnetizing field of strength which isreadily produced in practice and in such thickness is capable oftransmitting electromagnetic waves, for example in the centimeter range,with verysmall attenuation. Suitable means for producing the necessarylongitudinal magnetic field surrounds element 24 which means may be, forthe purpose of illustration, a solenoid 27 mounted upon the outside ofguide 12 and supplied by a source 28 of energizing current. It should benoted, however, that element 24 may be permanently magnetized. The angleof rotation of polarized electromagnetic waves in such magnetic materialis approximately directly proportional to the thickness of the materialtraversed by the waves and to the intensity of the magnetization towhich the material is subjected, whereby it' is possible to adjust theamount of rotation by varying or properly choosing the thickness ofthematerial. comprising element 24 and the intensity of magnetizationsupplied-by solenoid 27 In. the simplified view of the phenomenoninvolved as offered'in saidHogan application, a plane polarizedwave.incident upon the magnetic material in the presence of themagnetic fieldproduces two sets of secondary Waves in: the material, each setofsecondary waves being circularly polarized; The two sets of secondarywaves are circularly polarized in opposite senses and they travel.throughxthe'medium at unequal speeds. Upon emergence from the materialthe secondary waves in combination set up a plane-polarized wave, whichis in general polarize'd at'a different angle from the original'wave. Itshould be notedthat the Faraday rotation depends for its. direction uponthe direction of the magnetic field. Thus, if. the direction of themagnetic field is reversed, the directionof the Faraday rotation is alsoreversed in 'space while; retaining its original relationship to the"direction of the field.

The operation of the directional phase shifter of Fig. 1 may beconveniently explained with reference to the. dia.-- gram of Fig. 2'.Thus, a vertically polarized wave intro d'uced. at terminal A into guide11 travelspast vane 14 unaffected thereby inasmuch as the plane of thevane is perpendicular to the polarization of the wave, and pasttransition member 26, to element 24. The thickness of element 24 and thepotential from source 28 are adjusted as pointed out hereinbefore togive a 45 degree rotation of the plane of polarization in the samedirection as the angle existing between guide 11 and guide 13. Thus, as

. shown in Fig. 1, the polarization of the wave is rotated 45 degrees ina clockwise direction, as indicated by the arrow on element 24 in thedrawing, thereby bringing the plane of polarization at right angles tothe plane of vane 19, the preferred direction for unaffectedtransmission past vane 19 and into the preferred polarization. forpassage through guide 13 to terminal B. This straight through passage ofwave power from terminal A to terminal B is illustrated on Fig. 2 byline 36. On the other hand, a vertically polarized wave applied atterminal B to guide 13 passes vane 19, is rotated 45 degrees by element24 in the direction of the arrow thereon, bringingthe wave into apolarization parallel to the plane of vane 14. This passage is indicatedby line 37 on Fig. 2. In view of this polarization, vane 14 reflects thewave back to element 24 which again rotates its polarization 45 degreesin the direction of the arrow bringing the wave into a polarizag tionparallel with the plane of vane 19. This passage is indicated by line 38on Fig. 2. Vane 19, therefore, reflects the wave again through element24 where it receives a further 45 degree rotation in the direction ofthe arrow, bringing its plane of polarization perpendicular to.

the plane of vane 14 and into the preferred direction fortransmissionpast vane 14 and through wave guide 11 to terminal A. This passage isindicated by line 39 on Fig. 2.

Assuming an initial polarization of the wave as that in guides 11 and 13for its passage from terminal A to terminal B, it will be seen that onpassage from terminal B to terminal A the wave leaving guide 11 hasbeenin.- verted or has experienced a phase delay of 11- degrees with respectto the assumed initial polarization. This phase inversion is indicatedon Fig. 2 by'an. element 40 introducing a phase delay of 1r. It is thusreadily seen from Fig. 2 that the Wave on passing from terminal B toterminal A has traveled along a path longer by the addition of Zea thanthe path from terminal A to terminal B and'has in addition experienced aphase inversion of ar. Thus, by regulating the longitudinal positions ofvanes 14 and 19 in guide 12, the distance or and the correspondingunidirectional phase shift 20c+1r may be arbitrarily chosen.

Fig. 3 shows an embodiment in accordance with the invention, whereby afirst arbitrary value of phase shift is introduced to microwave energytraveling from terminal A to terminal B, and a second and diflerentpredetermined value ofphase shift is introduced in traveling fromtermi-- nal B to terminal A. The directional phase shifter of Fig. 3comprises a rectangular wave guide 46 which sup? ports a verticallypolarized wave, tapering into a round wave guide 47 to which is joinedby a shuntplane junction a. second rectangular wave guide 48perpendicular to both guides 46 and 47 which guide 48 will acceptonly'horizontally polarized waves. Thus, guides 46 and 48 comprise apair of conjugately related terminals or branches. in that a wavelaunched in either one will not appear at the other. A highly conductivereflecting vane 49 is preferably placed in circular guide 47 oppositethe junction. aperture of guide 48 to reflect into guide 48 those. waveshaving their plane of polarization coincident with the plane of vane 49.The spacing between vane 49 and the aperture of guide 48.may be adjustedto give maximum power transfer in this circuit. At a point to: the rightof guide 48 along guide 47 is'a Faraday-effect rotator comprising;element 24, its associated conical members 25 and 26, and means forsupplying a magnetic field 27, the last-named components beingsubstantially identical to those bearing corresponding. referencenumerals in Fig; 1, described hereinbefore. At distances polarization ofa wave in guide 46. Vanes 50 and 51 i are each adapted for longitudinalposition adjustment along the length of guide 47 in the same manner aswer vanes 14 and 19 of Fig. l. Thus, guides 46 and 48 comprise a pair ofpolarization-selective connecting terminals by which wave energy in twoorthogonal TEn mode polarizations may be coupled to and from one end ofguide 47. Vanes 59 and 51 constitute a second pair ofpolarization-selective reflecting terminations at the other end of guide47 by which each of the two orthogonally related TE11 modes in guide 47which have their planes of polarization respectively related by 45degrees to the planes of polarization to which guides 48 and 46 arecoupled, are reflected back along the length of guide 47. As willbeshown hereinafter with respect to Fig. 3A, the wave energy in thoseplanes of polarization may be reflected by members coupled in differentways to the proper planes in guide 47.

The operation of the directional phase shifter of Fig. 3 can beconveniently explained with reference to the diagram of Fig. 4. Thus, avertically polarized Wave introduced at terminal A into guide 46 travelspast vane 49 unaffected thereby inasmuch as the plane of the vane isperpendicular to the polarization of the wave, and travels past theaperture of guide 48 to element 24. Thethickness of element 24 and themagnetic field applied thereto are adjusted to give a 45 degree rotationin a clockwise direction, as indicated by the arrow on element 24 in thedrawing. Thus, the wave emerging from element 24 is brought into a planeof polarization at right angles to vane 50, the preferred direction fortransmission past vane 50, and into the plane of vane 51. This passageof wave power is indicated by line 61 on Fig. 4. In view of thepolarization of the wave at vane 51, the wave is reflected back towardelement 24, again passing vane 50. Element 24 rotates its polarization45 degrees in the direction of the arrow bringing the wave into apolarization parallel with vane 49 which reflects it into guide 48 withthe proper polarization for passage to terminal B. This passage isindicated by line 62 on Fig. 4.

On the other hand, a horizontally polarized wave applied at terminal Bto guide 48 is reflected by vane 49 toward element 24which rotates thepolarization 45 degrees in the direction of the arrow bringing thepolarization of the wave into the plane of vane 50. This passage isindicated by line 63 on Fig. 4. Vane 50, therefore, reflects the waveagain through element 24 where it receives a further 45 degree rotationin the direction of the arrow bringing its plane of polarizationperpendicular to the plane of vane 49 and into the preferred directionfor transmission past vane 49 and through wave guide 11 to terminal A.This passage is indicated by line 64 on Fig. 4.

As in the phase shifter of Fig. 1, if an initial polarization of thewave is assumed as that in guides 46 and 48 for its passage fromterminal A to terminal B, it will be seen that on passage from terminalB to terminal A, the wave leaving guide 46 has been inverted or hasexperienced a phase delay of 1r degrees with respect to the assumedinitial polarization. This phase inversion is indicated on Fig.4 by anelement 65 introducing a phase delay of 1r. If the relative path lengthsfrom terminal A to terminal B, and from terminal B to terminal A, arecompared by measuring the distances to the reflecting vanes 51 and 50,respectively, from an arbitrary point common to each path, such as apoint at section ZZ, it will be seen that the path from terminal A toterminal B depends upon a distance 2,8, it being the distance fromsection Z--Z to reflecting vane 51, and that the path from terminal B toterminal A depends upon a distance 2oz+1r, a being the distance fromsection ZZ to reflect- V 6 ing vane 50. Thus, by separately regulatingthe longitudinal positions of vanes 50 and 51 in guide 47, a firstarbitrary value of phase shift 2 8 may be introduced to microwave energytraveling from terminal A to terminal B, and a second and differentarbitrary value of phase shift 2a+1r may be introduced to microwaveenergy traveling from terminal B to terminal A. It should be noted thatwhile, as shown in the drawings, the distance or is smaller than thedistance 3, this relationship may be reversed without affecting theoperation of the phase shifting device so long as the respective planesof orientation of vanes 56 and 51 are not changed.

Fig. 3A shows an alternative modification of Fig. 3 having phaseshifting properties identical to those of the device of Fig. 3, whichproperties have been shown in Fig. 4. According to the modification ofFig. 3A, round wave guide 47 tapers into a rectangular wave guide 72which supports a wave polarized in a plane inclined 45 degrees withrespect to the polarization of a wave guide 46. Guide 47 is joined in ashunt plane junction by a second rectangular guide 71 which isperpendicular to both guides 47 and 72 and which will accept waves fromguide 47 having a plane of polarization inclined at 45 degrees to thepolarization of those waves accepted by guide 48. A highly conductivereflecting vane 75 is positioned with respect to the aperture of guide71 and bears the same relation thereto as vane 49 to the aperture ofguide 43. Thus, guide 71 accepts those waves formerly reflected by vane50 of Fig. 3, and guide 72 accepts those waves formerly reflected byvane 51 of Fig. 3. Shorting pistons 73 and 74 terminate guides 71 and72, respectively, in a reflecting manner and the position of thesereflecting pistons along the guides 71 and 72 determines the values ofthe relative delays at and 5, respectively, as shown on Fig. 4.

While the two directional properties of the phase shifting devices inaccordance with the present invention have been primarily stressedherein, it should not be overlooked that the disclosed structures mayalso serve to introduce a desired. value of phase shift into a systemconveying energy in only one direction. In such a system two preadjustedvalues of phase shift may be alternately inserted in the system merelyby reversing, either by hand or by suitable switching means, thedirection in which the energy traverses the disclosed phase shiftingdevices.

In the particular case in which the phase shift in one direction isdegrees different from the phase shift in the other direction, thepresent phase shifting devices then exhibit the properties of thecircuit element known as a gyrator, for which numerous applications aredisclosed in said copending Hogan application and in the publicationsreferred to therein.

A further embodiment of a unidirectional phase shifting device havingproperties identical to those of Fig. 1 herein may be obtained byterminating in a reflecting manner the branches 0 and d of the fourbranch switching system disclosed in Fig. 9 of said copending Hoganapplication. A further embodiment having phase shifting propertiesidentical to those of the phase shifter of Fig. 3 may be obtained byterminating in a reflecting manner terminals b and d of the four branchswitching system disclosed in said Fig. 9.

In all cases, it is understood that the above-described arrangements aresimply illustrative of a small number of the many possible specificembodiments which can represent applications of the principles of theinvention. Numerousand varied other arrangements can readily be devisedby those skilled in theart without departing from the spirit and scopeof the invention.

What is claimed is:

1. A non-reciprocal phase shifting device for electromagnetic waveenergy comprising a section of circular wave guide, a pair of conjugatemicrowave connections coupled to one end of said guide for wave energypolarized in orthogonal planes therein, a pair of highly conductivediametrical vanes disposed in the other end of said guide,

2,7 l., 11:7. '1 I I 1 C l :said vanes lying inplanesperpendicular toeach other and 'at 45 degrees to the orthogonal planes to which saidconnections are coupled; and an antireciprocal rotator for producing a45 1 degree Faraday-effect rotation disposed in'said circular guidebetween said one end and said other end. F 2. A non-reciprocalphase'shifting device for electromagnetic wave-energycomprising awave-guide section having a characteristicimpedance and adapted tosupport said energy in orthogonal polarizations, a pair ofpolarization-selective wave-guideconnections at one end of said guideeach-adapted to couple to and from one orthogonal polarization of waveenergy' in-said one end; -a pair of wave-guide =reflectingterminations-Iat the other end of said guide; each of said ter'mination's presenting acharacteristic impedance-substantially different from said guidecharacteristic-impedance to-wave energy having an orthogonalpolarization respectively-relatedby'a given angle to a polarization insaid. one end, and means for producing a polarization -rotationinterposed in said guide between said ends, said means producing'anangle of rotation in the same sense as viewed'in the direction ofpropagation of wave energy through said guide for opposite directions ofpropagation therethrough which is equal to said given angle.

3. A device in accordance with claim 2, wherein said given angle isequal to- 45 degrees. 4.- A- phase shifting device for electromagneticwave energy comprising a section ofcircular wave guide, apair ofwave-guide connections located at one end of said guide to couple waveenergy to 'and fro'rnsingle planes of polarization in said guide,apairofreflecting-members located at the otherend of said guide to'present a substantially short circuit to wave energy incident upon saidmembers -in-planesof polarization, the planes of said members beingdifferent from-each other and from the planes to which said connectionsare'coupled, and means including a polarization rotator interposed inthe path of wave energy between said connections and said members forproducing a-polarization rotation of wave energy prop= agatedfrom saidone end to said other end equal'to the angle between the particularplane of one of'said members and the plane to which one ofsaidconnections is coupled and of wave energy propagated from said other'end to said one end equal to the angle between said particular planeand the plane to which-the other of said connections is coupled whereby'wave'energy applied to said one con nection'is rotated'intothe plane ofreflection of said one member and hence in-to the plane ofsaid otherconnection.

5. A non-reciprocal phase shifting device for electro' magnetic waveenergy comprising a section of circular wave guide adaptedto-support'said energyin orthogonal polarizations, a first pair oforthogonal polarization-selective'wave-guideconnections at one end ofsaid guide each adapted to couple to and from one orthogonalpolarization ofwave energy in said one end, a second pair of orthogonalpolarization-selective wave-guide connections at the other end of saidguide. each adapted to couple to and from orthogonal polarizationsrespectively related by a given anglefltora polarization-insaid oneend,- means for producing a polarization rotation interposed insaidguide between said ends, said-means having an angle of rota-I tion; inthe same-sense as viewed :in .the direction -'of propagation of waveenergy--through said:guide for op-' nated in a-reflecting terminationhaving high reflection properties and lowabs'orptioni properties bywhich said energy is reflected backto-said guide. t Y

6. A non-reciprocal phase shifting device for producinga givendiflerential phase shift for opposite directions of propagation'ofelectromagnetic wave energy there- -through comprisinga section ofcircular wave guide, a first pair of orthogonal wavepolarization-selective termini coupled to one portion-of said guide, asecond pair of orthogonal wavepolarization-selective termini coupled toanother portion of said guide, and an antireciprocal rotatorforproducinga Faraday-effect rotation'of linearly polarized \vaveenergyinterposed betweensaid portions, two' of said termini being each aconnecting terminal by which said energy may be coupled to and from saidguide, the-remaining two of'said termini being each a reflectingtermination having high reflection properties and low absorptionproperties by which 'said energy is reflected along said guide,at'le'ast one of said reflecting termini being movable with respect tothe other of said reflecting termini for providing an adjustableelectrical distance therebetween which'is equal to a function of saidgiven differential phase'shift.

7. 'A' device for'producing a predetermined diiferential phase shiftin"elect'romagn'etic wave energy for opposite directions of propagationtherethrough comprising a sec tioh of Wave g'uide'capable of supportingsaid wave energy in 'four polariza'tio-n'seach of which is ang'ularlydisplaced froni'the -adjacent ones by 45 degrees, an antireciprocalrotator interposed in said guide for antireciprocally rotating theenergy inany'one'of said'polarizatio'ns on one side ofs'aid'rotator'into a'nadjacent' one of said'polariz'ation'so'n theopposite side of said r'otator, a pair of polarization-selectivewaveguide connections to said guide coupled to said wave energy in twoof said polarizations, and means for presenting a movablepoint ofsubstantial short circuit to each of the remaining two of saidpolarizat'ions, said points being at an adjustable electrical distancepqsite vdirections of. propagation therethrough' .which-. is

equal to said given angle, two of said termini being termifrom eachotherwhich is equal to a function of said predetermined differentialphase shift.

8. A non-reciprocal phase shifting device for producing a givendifferential phase shift for opposite directions of propagation ofelectromagnetic Wave energy therethroughcomprising a section of circularwave guide, an antireciprocal rotator for producing a Faraday-effectrotation of linearly polarized wave energy interposed insaid guide, apair of wave polarization-selective wave guide connections coupled tosaid guide one on each side of said-rotator, and a pair of wavepolarization-selective reflecting-termini coupled to said guide one oneach side of said rotator, each of said reflecting termini having highreflection properties and low absorption properties for the wavepolarization orthogonal to the polarization coupled to the waveguide-connection on the same side of said rotator and at least one ofsaid reflecting termini being movable withrespect to the other of saidreflecting termini for providing an adjustable electrical distancetherebetween which is equal to a function of said given differ entialphase shift.

References Cited in the file of this patent UNITED STATES PATENTS1,742,115 Whittaker Dec. 31, 1929 2,441,598 Robertson= a hc; May 18,1948 2,607' 849 Purcell Aug-19, 1952 2,644,930 Luhrs July 7, 1953

